Identification of Intermediate Au-22(SR)(4)(SR ')(14) Cluster on Ligand-Induced Transformation of Au-25(SR)(18) Nanocluster

摘要

We report the ligand-exchange-induced transformation from an icosahedral Au-25(SR)(18) cluster (where SR = 2-phenyl-ethanethiol (PET)) to a bitetrahedral Au-22(SR)(4)(SR')(14) cluster (where SR' = 4-tert-butylbenzenethiol (TBBT)). This partial exchange of the ligands was achieved by controlling the concentration of the incoming TBBT ligand. Being a bulky and aromatic ligand, TBBT can efficiently distort the atomic structure of the Au25PET18 cluster, resulting in Au-22(PET)(4)(TBBT)(14), which is highly stable and considered to be an intermediate with a bitetrahedral structure. Time-dependent mass spectrometry and optical spectroscopy revealed the dissociation of the parent cluster and gave a deep insight on the ligand-exchange mechanism. Theoretical calculations and extended Xray absorption fine structure studies confirm the formation of the Au-22 structure. Identifying the atomic structure of the intermediate species opens a new avenue to study the transformation of one cluster to another.